Spark-gap construction



March 3,1931.

H. P. M LAGAN SPARK GAP CONSTRUCTION Filed July 2, 1927 INVENTOR. HECTOR P MAcLA a/w Z WM Z5. M

g yizg g A TTORNEY.

Patented Mar. 3, 1931 UNITED STATES PATENT OFFICE HECTOR P. MACLAGAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO M'CINTOSH ELECTRICAL CORPORATION, OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE SPARK-GAP CONSTRUCTION My invention relates to an improved construction of spark-gap for producing high frequency alternating current discharge for electro-therapeutic and other purposes, for

pxrpnple deep heating of the tissues of the ooc y.

My invention consists essentially of a plu rality of pairs of spark-gap contacts, one of each pair being mounted on an insulating 1o framework by which all of these contacts so mounted may be moved simultaneously relatively to the other contacts of the several pairs to produce a plurality of spark-gaps, the other contacts of the several pairs being 15 mounted on a second insulating framework and each provided with an adjusting handle for moving the corresponding contact relatively to the other contact of the same pair. By my construction I further provide de- '20 vices for moving the first framework referred to and all of the contacts carried by it, so that similar spark-gaps are produced simultaneously between the contacts of the several pairs. I further provide the device 2 with electrical connections arranged to connect the several spark-gaps in series with each other, since I find that this arrangement is more effective in producing high frequency discharge than where a single gap so is used having a length equal to the sum of the several gaps connected in series with each other; By my construction I mount the several gap contacts on substantial metal plates affording large areas for heat radiation, to

V 35 the end that theparts of the device may not 7 be overheated by the sparking action.

. lilyinvention will best be understood by reference to the accompanying drawings, showing a preferred embodiment thereof in 40 which Fig. 1 shows. my construction in side ele- .vat-ion; and partially in sectional view to show the operating mechanism, V Fig. 2 is a vertical sectional view of the i p'arts shown in Fig. 1 taken along the line j Fig. 3 shows in. plan View the upper and movable contact supporting framework, and I Fig. shows in plan view the lower and 59 fixed contact supporting framework,

Similar numerals refer to similar parts throughout the several views.

As shown in the drawings my device consists of end plates 10 and 11, preferably of metal held in separated relation by rods 12 and 13 of suitable insulating material, preferably having a high insulating value and resisting surface creepage as far as possible, which rods may be secured in any desired manner at their ends, for example by screws, to the end plates 10 and 11. The end plates 10 and 11 may be provided with feet 10a and 11a at their lower edges to afford a convenient support for the device and to facilitate mounting it as and where desired.

Between the upper portions of the end plates 10 and 11, I support a first framework 1 1 which, as more clearly indicated in Fig. 3, consists of side bars 15 and 16 of insulating material, for example lava, connected at their ends in suitable manner, for example by screws, with metal end bars 17 and 18. The bar 17 has projecting from its mid portion a metal rod 19 to enter a corresponding aperture in the end plate 11, which rod 19 is surrounded by a spring 20 held in compression between the bar 17 and the end plate 11. The mid portion of the bar 18 has projecting therefrom a metal rod 21, extending through a corresponding aperture in the end plate 10 and into a metal housing 22 secured to the outer surface of the end plate 10. The housing 22 is provided with a bore for supporting. a bushing 23 of insulating material sub 'stantially in axial alignment with the axis of the rod 21, which bushing is held in place in the housing 22 in any convenient manner, for example by screws as lndlcated. The 1nner end of the bore in the bushing 23 is of a size to receive with a free sliding fit a rod 2 1 of insulating material which rests against the endof the rod 21. The outer portion of the bore in the bushing 23 is threaded to receive a screw 25, the inner end of which may engage the outer end of the rod 24:. .The screw 25 is provided at its outer end with an operating head 26 by which the screw may be turned to move the framework 14 to the right, and when the screw 25 is turned in the opposlte direction by means of the head 26, the spring i on ' 20 serves to move the framework 14 to the left. In this manner any desired position may be given the framework 14 and the contacts carried'thereby. A collar 27 is preferably provide'd'onthe screw near its outer end,which is provided with a set screw 28 for securing the collar at any desired point on the screw 25toflimit motion to the right of the framework 14 and thus-secure any deends or metal bars '29, 29a, 29?), 290, 29a, 296,

129;. and 29g towhich bars the upper end of plates 30,3061, 30b, 30c, 30d, 306, 30; and 30;,

are respectively secured in any desired man-. ner, for-example by riveting. The bars 29 to 299 are rigidly held in the framework 14 so that'the plates 30 to 30; cannot readily be moved relatively to the framework, by threading theouter ends of the supporting projectionsof the bars 29 to 299 and screwnected electrically by .ametal plate 34 insideoffthe insulating bar 15; }and the bars29e and 29f are similarlyelectricallyconnected by a metal plat 35 -insidexof the insulating nuts tightly on said threaded ends, but one nut being used by each offthe bars; The 1 a arrangement further providesthat the bar 29 is rigidly secured to the insulating bar15,

that the bars 29a and 29?) are rigidly secured tothe insulating bar 16, that the bars 290 and 29d are rigidly secured tothe insulating bar" ""15, that the bars 296 and29fare rigidlysecured to the insulating bar 16,'and that the bar 299 is. secured to the insulating bar 15. As indicated in Fig.1, thenuts on the ends .of the bars29 and 299 form convenient means for making electrical contact with said bars by the terminal wires 31 and 32 of the device.

The bars 29a and 29?) are electrically connect- Ied bya metal plate .33 inside of the insulating bar 16 held in firm engagement with the bars 29a and 29b bythe nuts onthe endsof said bars ;the bars 290 and 29d are similarly conbar 16. The' end portions of the bars 29 to 299 are preferablyfshouldered to facilitate clamping the'bars and connecting plates tightly against the insulauting bars 15 and 16 in the manner described.

- The distance between the shouldered portion f h f the bars29' to 29 is preferably somewhat less "than the distanceibetween the inner surfaces of the insulating bars 15 and 16 so that no unduef strains are exerted on 'the framework '14 bytheheating of the bars29'to 29g and :plates 30to 309, the end extensions from the 'bars'29 to 29g not provided with clamping nuts being preferably a free. sliding fit in the hole's providedto receivethem.

1 As indicated in Figs. 1 and 2, the plates 30 to 30g are provided on the left hand sideof the mid-portions of their lower ends, w th contacts as, 36a, 36?), 360, 36d, 36(2: 3 and 369 respectively, which are preferably of of reduced diameter extending through the corresponding plates and threaded to recelve nuts as indicated.

Between the lower portions of the end plates 10 and 11, a-second framework 37 is diposed, of similar construction to the framework 14 excepting as to the manner of mounting it between the end plates 10 and 11 As shown in Fig. 4, the framework 37 consists of "insulatingsidebars 38 and 39 andmetal end bars 40 and 41, the frameworkbeing held in placebetween the end plates 10 and 11 by suitable screws 42, so that no movement of the 'frameworkis possible relatively tothe end plates. The bars 38 and 39 are provided with aligned holes for receiving-the shouldered ends of bars 43, 43a, 436, 430, 43d, 430,

43 and 43g and to these bars the lower edges of contact plates 44, 44a, 44b, 44c, 44d, 446, 44; and 449 are respectively secured, preferably by small screws and'nuts as indicated. hese screws are preferably'fitted in the contact plates and their supporting bars to permit a small amount of play of the contact plates relatively to the supporting bars and to hold the contact plates in place on the bars with a slightly yielding engagement. Thin 'flat'plates of suitable spring metal45, 45a, 456,450, 456L456, 45] and 45g respectively are-located on the bars 43 to 439, one of i said springplates' being disposed between each'of said bars and the pair of nuts used with it to hold the corresponding contact plate in place on it. i i The bars '43 to 439, are preferably shouldered at their ends as described for the bars '29 to 299, and the distance between their shouldered end'is somewhat less than the dis- 7 tance between the inner surfaces of the insulatingbars 38 and'39 for the purpose above barf39 and have rigidly secured to their'projecting ends respectively, handles '46 to 469 inclusive, of insulating material, for independently turning the bars 43 to 439 and the contact 'plates carried thereby, relatively to.

the framework 37. The bars 43 and 4364 are electrically connected by thin plate 47 of spring metal between their endshoulders and the innersurfaces of the insulating bars 38 and 39; theibars '43b and 430 are similarly connected by similar plates 48; the bars 43d and 436 are similarly connected bysimilar'plates 49; and the bars 43fand 43gIare similarly connected'by similar plates 50. Plates 60, 61, 62, and 63, similar to the platesf47, 48, 49 and 50 are disposed 7O tungsten and held in place by having portlons described for the bars 29 to 29g. 'The shoul- 'dered extensions of all of the bars 43 to 439 extend at oneend through the insulating on the extensions of the corresponding ones 'of the'bars 43 to 43g,between the handles 46 to 44g, carry at their mid-portions near their upper edges, contacts 54 to 549 similar to the contacts 36 to 369 above described and similarly secured to the corresponding supporting plates, these contacts being in alignment respectively with the contacts 36 to 36g, to cooperate'respectively with the contacts 36 to 36g to form the several spark-gaps. The cooperating faces of the contacts are preferably crowned to insure proper cooperation for different conditions of adjustment.

In using the device, I find it'desirable to i turn the screw 25 inwardly as far it will go against the action of the spring 20, to then move the contacts 54 to 549 against the contacts 36 to 369 by rotation of the handles 46 to 46g, to then turn the screw 25 in a direction to permit movement of the frame 14 by the action of the spring 20 as far as it will go, and then to turn the screw 25 to move the contacts 36 to 369 away from contacts 54 to 549 to give the desired separation between the contacts. The spring mounting of the contacts 54 to 54 insures their making proper contact with the corresponding rigid contacts and the mode of procedure described insures that all of the spark-gaps shall be of substantially the same length.

In Fig. 1 I illustrate diagrammatically the connection of the wires 31 and 32 to a source of high tension alternating current 55 and the connection of a condenser 56 to said wires. The combined action of the condenser 56 and thespark-gaps of the device is such that when the current is caused to jump the sparkaps by the impressed electromotive force, a igh frequency alternating current is produced due to oscillation of charge and discharge in the condenser 56. Current may be taken from this high frequency circuit for desired appllcation by wires 57 and 58.

From the above it will appear that desired degrees of separation of the contacts may be secured readily by my device, that the con struction is substantial and will not readily get out of order and that the heat developed at the spark-gaps is effectively disposed of by the large area plates carrying'the sparkgap contacts; also that substantially the same length of gap may be established at any spark-gap as at the other spark-gaps and that desired lengths of gaps may be definitely secured in any particular case by a corresponding setting of the stop collar 27 on the screw 25. i

While the plates 3030g and 44-449 may be made of any convenient size and shape to meet the requirements of any particular case, I find it preferable to corrugate them as shown in Fig. 1 to the end that they may have a maximum of cooling surface within the limited'dimensions of the device as a whole, required to make it convenient to use and readily portable.

Several most important advantages result from making and mounting the gap contacts as described. In the first place, the crowned ends of the contacts insure that at each gap the spark will be maintained for any particular adjustment, between the same two points on the two contacts of the gap, in-

stead of moving about on the sparking surfaces as occurs when they are plane surfaces; this prevents sparking at the edges of the ends of the contacts and avoids the edge pitting that occurs when edge sparking takes place due to the concentration of the current flow at the edges of the contacts. Again, the crowned sparking surfaces provide that the sparking will occur at the mid-portion of the crowned surfaces, regardless of the degree of separation of the contacts, it being borne in mind that each gap permitted by this device is but a part of an inch; in this way undue heating and pitting of the contacts is avoided. Again, the contacts are secured in fixed relation, to their mounting plates, which prevents any displacement of the contacts of any pair, relatively to each other, around the axes of the contacts, and maintains a constant and uniform sparking condition and relation at any pair of contacts, for any particular adjustment whenever the latter is used, even though the con tacts may be used in other positions between uses of that particular adjustment.

The described manner of mounting one contact of each pair for independentmovement, permits the fixed relative relation re ferred to, between the contacts of each pair, and at the same time permits independent movement of one of the contacts bodily towards and from the other contact of the pair, always maintaining the sparking points at the mid-portions of the crowned surfaces; it also permits locating the adjusting dev1ces involved in said'independent movement, at a considerable distance from the contacts, out of the highly heated Zone resulting from the sparking action, which could not be done were the contacts movable relatively to their mounting plates for purposes of individual adjustment.

The features of construction just referred to not only greatly facilitate the operation of the device, but they also combine to insure permanence, dependability and uniformity of operation to a high degree.

While I have shown my invention in the particular embodiment above described, it will be understood that I do not limit myself to this exact construction as I may employ equivalents known to the art at the time of the filing of this application without departingfromthescope of the appended mm:

' framework, a second'insulating framework carried by said support and fixed relatively thereto, second spark-gap contacts carried by said second framework and each cooperatingwith one of sald first contacts to form 'a' spark-gap, devicesfor moving said first frameworkto form as many spark-gaps of desired length as there are ofsaid firstcontacts, and metal conductors connecting said spark-gaps in series with each other, said second contactsbeing individually movable relatively to said secondframework to per-' mit' independently moving said second con-- tacts into engagement with corresponding ones of said first contacts for different positions' of said first framework.

' tacts,

"spark-gaps in series with each other, shafts 2 In a spark-gap,fthe combination of a support, a first insulating framework carried by said support and movable relatively thereto, firstspark-gapcontacts carried by said framework, a second insulating framework carried by said support and fixed relatively thereto, second spark-gap contacts carried by said second framework and each cooperating with one of said first contacts to form a spark-gap, devices for moving said first framework to form as many spark-gaps of desired length as there are of said first conmetal conductors connecting said mounted for turning. movement in said second framework and each carrylng eccentrically one of said second contacts, and a handle of insulating material secured to each of said shaftso p 3. In a spark-gap, the'comb-ination of a support, a firstinsulating framework carried by said support and movable relativelythereto, first spark-gap contacts carried by said frameworlna second insulating framework carried bysaid support'and fired relatively thereto, second s park-gap contacts carried by said'second framework and each cooperating with one:of said first 'contacts to form a spark-gap, devices for moving said first framework to form as many spark-gaps of desiredlength as there are of said first contacts, metal conductors connecting said spark-gaps in series with eachother, and a metal plate having larg'e'radiating surface supportingreach contact, said contacts'comprising blocksof tungsten secured to said plates screws and nuts for replacement purposes and having crowned gap surfaces,

4.111 'aspark-gap, the combination of a support, a first insulating framework carried by s'ai dsupport and movable relatively thereto, first spark gap contacts'carried by said framework, asecond insulating framework carried by said support and fixed relatively thereto, second spark-gap contacts carried by said second framework and each cooperating with one of said first contacts to form a spark-gap, devices for moving said first 'framework'to formxas 'many spark-gaps of desiredlengthasthere are of said first contacts, metal conductors connecting said spark-gaps in series with each other, a metal plate having large radiating 'surface eccentrically supporting each contact, shafts mounted for turning movement in said second framewor and each secured to one of said metal plates, and a handle of insulating material securedto eaohof said shafts.

5.111 a spark-gap, the combination of a support, a first insulating'framework carried by said support and movable relatively tively thereto, second spark-gap contacts carried bysaid second framework and each cooperating with one of said first contacts to form a spark-gap, devices for moving said first framework to form as many spark-gaps of desired: length as there are of said first contacts, metal conductors connecting said spark-gaps in series with each other, a metal plate having large radiating surface supporting each contact, shafts mounted for turning movement in said second framework and each secured to one of said metal plates, a handle ofinsulatingmaterial secured to each of said shafts, and a yielding device connecting each of said shafts withtheplate carried thereby, T 1 j 6 In a spark-gap, the combination of a support, a first insulating framework carried by said support and movable relatively thereto, first spark-gap contactscarried by framework, a second insulating framework carried by said support and fixed relatively thereto, second spark-gap contacts carried by said second framework and each cooperating with one of said first contacts to form a spark-gap, devices for moving said first framework to form as manyjspark-gaps of I screw threads engaging said screw.

- '7. Inspark-gap, thecombination of a support a first insulating framework carried "by said support andmovable relatively thereto, firstisp'ark-igap-contacts carried by said framework, a second insulating framework earned by said support and fixed relatively v; thereto, second'sp'ark-gap contacts carried by said second framework and each cooperating with one of said first contacts to form a spark-gap, devices for moving said first framework to form as many spark-gaps of desired length as there are of said first contacts, and metal'conductors connecting said spark-gaps in series with each other, said devices comprising a sliding'insulating rod engaging said first framework, a metal screw engaging said insulating rod, a handle secured to said screw, a housing extending from said support, and a sleeve of insulating material extending from said housing and having a bore loosely containing said insulating rod and screw threads engaging said screw. V

8.- In a spark-gap, the combination of a support, a first insulating framework carried by said support and movable relatively thereto, first spark-gap contacts carried by said framework, a second insulating framework carried by said support and fixed relatively thereto, second spark-gap contacts carried by said second framework and each cooperating with one of said first contacts to form a sparkgap, devices for moving said first framework to form as many spark-gaps of desired length as there are of said first contacts, and metal conductors connecting said spark-gaps in series with each other, said devices comprising a sliding insulating rod engaging said first framework, a metal screw engaging said insulating rod, a handle secured to said screw, a housing extending from said support and having a clearance opening for said insulating rod and carrying screw threads engaging said screw, and a spring tending to oppose the action of said screw.

9. In a spark-gap, the combination of a support, a first insulating framework carried by said support and movable relatively thereto, first spark-gap contacts carried by said framework, a second insulating framework carried by said support and fixed relatively thereto, second spark-gap contacts carried by said second framework and each cooperating with one of said first contacts to form a spark-gap, devices for moving said first framework to form as many spark-gaps of desired length as there are of said first contacts, and metal conductors connecting said spark-gaps in series with each other, said devices comprising a sliding insulating rod engaging said first framework, a metal screw engaging said insulating rod, a handle secured to said screw, a housing extending from said support, a sleeve of insulating material extending from said housing and having a bore loosely containing said insulating rod and screw threads engaging said screw, and a spring tending to oppose the action of said screw.

10. In a spark-gap, the combination of a support, a first insulating framework carried by said support and movable relatively thereto, first spark-gap contacts carried by said framework, a second insulating framework carried by said support and fixed relatively thereto, second spark-gap contacts carried by said second framework and each cooperating with one of said first contacts to form a spark-gap, devices for moving said first framework to form as many spark-gaps of desired length as there are of said first contacts, metal conductors connecting said spark-gaps in series with each other, and a corrugated metal plate having large radiating surface supporting each contact.

In witness whereof, I hereunto subscribe my name this 24th day of June, A. D. 1927.

HECTOR P. MAoLAGAN. 

